Abstract

We report on the buffer/absorber interface formation in highly efficient (14.5%, air mass 1.5) solar cells with a physical vapor depositedCdS buffer. For Se-decapped (CIGSe) absorbers we observe sulfur passivation of the CIGSe grain boundaries during CdS growth and at the interface a thermally stimulated formation of a region with a higher band gap than that of the absorber bulk, determining the height of the potential barrier at the interface. For air-exposed CIGSe samples the grain boundarypassivation is impeded by a native oxide/adsorbate layer at the CIGSe surface determining the thermal stability of the potential barrier height.